Preparations, characterizations, thermal and flame retardant properties of cotton fabrics finished by boron-silica sol-gel coatings

This work aims to improve the thermal stability and flame retardancy of cotton fabrics by using sol-gel processes. A hybrid sol was prepared by using silica sol, coupling agent of γ-Methacryloxypropyltrimethoxysilane (KH570) and flame retardant of sodium octaborate tetrahydrate (DOT) and then finished on the surface of cotton fabric. Fourier infrared spectroscopy (FTIR), X-ray electron spectroscopy (XPS), scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDX), thermogravimetric analysis (TGA), limiting oxygen index (LOI) and vertical burning test (VBT) were used to characterize the functional groups, surface element compositions, microscopic morphologies, thermal stability and flame retardancy of cotton fabrics, respectively. The results show that sols are successfully converted into gel coatings onto cotton fabrics. SiO2[email protected] shows the highest char residue rate (41.7%) and ΔLOI/Δm (6.0%/g) values. SiO2, KH570 and DOT coatings have shown some competitive but more synergistic effects in flame retardancy. The three-dimensional structure of SiO2 gel can provide structural support, effectively block heat transfer and transports of oxygen. KH570 has a significant coupling effect of increasing interfacial compatibility between sols and cotton fabrics. DOT is thermally decomposed to generate boric acid to accelerate the carbonization degrees of cotton fibers and thus improve the thermal stabilities of char layers.